1. Field of the Invention.
The present invention relates generally to a control circuit for a pump motor, and more particularly to a liquid level control circuit which automatically maintains the liquid level in a reservoir within a predetermined range.
2. Description of the Related Art.
Previous liquid level controlling devices typically include three separate assemblies: a reservoir assembly, a pump assembly, and a main control board. The reservoir assembly uses a magnet float/magnetic reed switch configuration to sense the level of liquid in the reservoir. Three magnetic reed switches situated within the reservoir at different levels provide signals to the main control board when the liquid level brings the magnetic float into proximity with the switches. These signals activate and deactivate a separately packaged, thermally protected, electrically isolated pump to adjust the liquid level. The main control board uses a power transformer to derive power for its electronics and an electromechanical relay to activate and deactivate the pump. An additional electromechanical relay is used to activate an alarm circuit when the liquid level reaches a predetermined level. This transformer/multiple relay configuration results in substantial power consumption, even in a standby condition when the pump is not active.
The present invention provides a liquid level controller having a reservoir assembly and a control board/pump assembly. The reservoir assembly includes sensors which sense the liquid level in the reservoir and provide signals to the control board/pump assembly indicating the liquid level. The control board/pump assembly includes a control circuit having a line voltage rectifier and two separate resistive power supplies. One supply powers the pump control circuit. The other supply is used to activate an alarm through an alarm relay, but only consumes power when the alarm is activated. A solid-state MOSFET transistor and a CMOS logic gate activate and deactivate the pump and provide the necessary pump hysteresis. This solid-state circuit is reliable in operation and consumes low power during pumping and when in the standby condition.
The present invention provides a circuit for maintaining the level of liquid in a reservoir by controlling the operation of a pump for removing liquid from the reservoir in response to a start signal from a liquid level sensor indicating that the liquid level is outside a desired range. The circuit includes a resistive power supply to power the circuit, a logic gate for outputting a pump signal in response to receipt of the level signal, and a transistor coupled between the logic gate and the pump. The transistor enables the pump in response to receipt of the pump signal.
The present invention further provides a controller for a liquid reservoir having a sensor disposed within the reservoir. The sensor outputs a start signal indicating a level of the liquid in the reservoir. The controller includes a control circuit coupled to the sensor for receiving the start signal, and a non-isolated pump connected to the control circuit. The pump adjusts the liquid level when activated. The control circuit activates the pump in response to receipt of the start signal.
The present invention further provides a controller for a device having a liquid reservoir and an alarm, including a first resistive power supply for converting an AC power input to a first DC voltage, a logic circuit powered by the first DC voltage, a non-isolated pump coupled to the logic circuit, a second resistive power supply for converting the AC power input to a second DC voltage, and an alarm circuit using the second DC voltage to activate the alarm.